The invention pertains to methods of forming patterned constructions, such as methods of patterning semiconductive substrates. In a particular aspect, the invention pertains to methods of forming field emission displays.
Modern semiconductor fabrication processes frequently involve patterning of materials. One common method of patterning is to form a layer of photosensitive material (e.g., photoresist) over a substrate and expose the material to a source of radiation. A mask is provided between the radiation and the photosensitive material, with the mask comprising opaque and transparent regions. The mask patterns the radiation passing through it, and the patterned radiation impacts the photosensitive material to create a pattern of exposed and unexposed regions. The exposed regions are rendered either more or less soluble in a solvent than the unexposed regions. After the exposure to the patterned beam of radiation, the solvent is utilized to selectively remove either the exposed or unexposed portions of the photosensitive layer and to thereby transfer a pattern from the mask onto the photosensitive layer. If the exposed portions are removed a positive image of the mask is formed in the photosensitive layer, and if the unexposed portions are removed a negative image of the mask is formed in the photosensitive layer.
The above-described processing is frequently referred to as xe2x80x9cphotolithographic processingxe2x80x9d. It is utilized for forming numerous patterned constructions for semiconductor devices. A difficulty with the method is that a resolution of the method can be limited by properties of the photosensitive material and optics of the pattern transfer tools. Accordingly, it would be desirable to develop improved methods of photolithographic processing, such as, for example, developing improved photosensitive materials.
In another aspect of the prior art, field emitters are used in display devices, such as, for example, flat panel displays. Emission current and brightness of a field emission display is a function of a number of factors, including emitter tip sharpness. Specifically, sharper emitter tips can produce higher resolution displays than less sharp emitter tips. Accordingly, numerous methods have been proposed for fabrication of very sharp emitter tips (i.e., emitter tips having tip radii of 100 nanometers or less). Fabrication of very sharp tips has, however, proved difficult. It has proved particularly difficult to build large areas of sharp emitter tips using the above-described photolithographic methods while maintaining resolution and stringent dimensional control over large area substrates used for display manufacture. A technology that has been proposed for enabling formation of emitter tips is a particle dispersment technology (such as the process of U.S. Pat. No. 5,676,853 to Alwan) wherein small particles are layered over a substrate to form a mask for formation of emitter tips. Thus far, the dispersment technologies have proved difficult to utilize in that it is difficult to stringently control the location of emitter tips formed from the somewhat random distribution of particulates over a substrate surface.
In light of the above-discussed difficulties, it would be desirable to develop alternative methods for forming emitter tips.
In one aspect, the invention includes a method of patterning a substrate. A film is formed over a substrate and comprises a plurality of individual molecules. The individual molecules comprise two ends, with one of the two ends being directed toward the substrate and the other of the two ends being directed away from the substrate. Particle-adhering groups are bound to said other of the two ends of at least some of the individual molecules, and a plurality of particles are adhered to the particle-adhering groups. The adhered particles are a mask over the substrate. The substrate is etched while the mask protects portions of the substrate.
In another aspect, the invention encompasses a method of forming a field emission display. A material is formed over a substrate. The material has a surface with exposed nitrogen-containing groups. At least one portion of the material is exposed to radiation while leaving at least one other portion of the material unexposed. The exposing renders one of the exposed or unexposed portions better at bonding the masking particles than the other of the exposed and unexposed portions. After the exposing, the material is bonded with masking particles. The bonding comprises reacting exposed moieties of the masking particles with the nitrogen-containing groups. The adhered masking particles define a mask over the semiconductive substrate. The substrate is etched while the mask protects portions of the substrate. A plurality of emitters are formed from the substrate. A display screen is provided to be spaced from the emitters.